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981.
通过溶液法在含硅芳炔树脂(PSA)中加入催化剂乙酰丙酮镍和三苯基膦,制备了碳纤维增强PSA复合材料(T700CF/PSA),研究PSA树脂的热自聚固化和催化固化反应动力学、固化树脂的热性能和复合材料的弯曲性能。结果表明:PSA中加入催化剂可降低其固化温度,初始表观活化能下降,但后期固化表观活化能提高。加入催化剂后的PSA的热稳定性略高于未加催化剂的PSA,800℃氮气氛围中残留率达88%。单向碳纤维T700CF增强PSA基复合材料室温下的弯曲强度为1 805 MPa,弯曲模量为149 GPa,300℃下弯曲强度和弯曲模量的保留率分别为73%和93%,其玻璃化转变温度高于500℃。T700CF增强含催化剂的PSA基复合材料的弯曲模量提高,但室温下弯曲强度略有降低。 相似文献
982.
983.
984.
叶顶结构型式对轴流风机性能、噪声及叶片静力特性等均有一定影响。以OB-84型带后置导叶的轴流式通风机为对象,采用Fluent数值模拟软件及Ansys有限元分析模块,通过比较开槽前后风机轴功率的变化探讨双凹槽叶顶结构的节能效果,分析了原叶顶及双凹槽叶顶下风机噪声及叶片的静力结构特性。研究表明:双凹槽叶顶下风机轴功率有所下降,设计工况下轴功率较原叶顶时下降了3.96%,可在一定程度下降低风机的能耗;双凹槽叶顶下风机噪声有较大幅度提高,设计工况下噪声较原叶顶时增长约14.88%,给风机正常运行带来不利影响;不同叶顶下叶片的静强度校核结果均满足要求,即采用双凹槽叶顶结构不会引起叶片的变形及断裂失效。 相似文献
985.
Xinyuan Ke Susan A. Bernal Nan Ye John L. Provis Jiakuan Yang 《Journal of the American Ceramic Society》2015,98(1):5-11
In this study, one‐part “just add water” geopolymer binders are synthesized through the alkali‐thermal activation of the red mud which is relatively rich in both alumina and calcium. Calcination of the red mud with sodium hydroxide pellets at 800°C leads to decomposition of the original silicate and aluminosilicate phases present in the red mud, which promotes the formation of new compounds with hydraulic character, including a partially ordered peralkaline aluminosilicate phase and the calcium‐rich phases C3A and α‐C2S. The hydration of the “one‐part geopolymer” leads to the formation of zeolites and a disordered binder gel as the main reaction products, and the consequent development of compressive strengths of up to 10 MPa after 7 d of curing. These results demonstrate that red mud is an effective precursor to produce one‐part geopolymer binders, via thermal and alkali‐activation processes. 相似文献
986.
The effect of power ultrasound on physicochemical properties and oxidative stability of an interesterified soybean oil (IESBO) was investigated. IESBO was crystallized at 32 °C and sonicated for 10 s with acoustic power of 101 W. The sonicated IESBO was tested for melting behavior and chemical composition and compared to those of non sonicated IESBO to determine physical and chemical changes originated as a consequence of sonication. Application of power ultrasound affected the melting behavior of the crystallized fat and did not affect its chemical composition. Oxidation stability of the sonicated IESBO was measured using peroxide value (PV) and compared to that of non sonicated IESBO and liquid soybean oil (SBO) when stored at 25 °C for 105 days followed by storage at 40 °C for 42 days. Power ultrasound did not cause accelerated oxidation in SBO or IESBO until they were highly oxidized (PV > 10 mequiv/kg). At high levels of oxidation, non‐sonicated IESBO had significantly higher PV than sonicated IESBO, while non‐sonicated SBO had significantly lower PV than sonicated SBO. 相似文献
987.
针对永磁同步电机转子初始位置检测已有方法存在的电机"抖动"、对电机参数依赖性强、高频电流信号数学处理算法复杂等问题,提出一种基于高频电压信号注入法的永磁同步电机转子初始位置检测方法。该方法通过对三相高频电压信号的电流响应进行低通滤波,比较三相电流响应幅值的大小关系,依据转子位置角θ对三相高频电流响应信号幅值的调制规律,得到电机转子初始位置信息,最后利用电机磁路饱和效应区分电机转子NS极性。理论分析及实验表明,该方法能准确检测出电机转子初始位置信息,电机转子不会发生"抖动",检测方法对电机参数依赖性低,电流处理算法简单,不需要额外增加硬件电路,检测误差较小,可满足永磁同步电机的平稳起动要求。 相似文献
988.
Synthesis and characterization of biodegradable polyurethanes with unsaturated carbon bonds based on poly(propylene fumarate) 下载免费PDF全文
The segmented polyurethanes synthesized from biodegradable polyesters are very promising and widely applicable because of their excellent physiochemical properties. Poly(propylene fumarate) (PPF), a kind of linear aliphatic unsaturated and biodegradable polyesters, has been well recognized in biomedical applications. Herein novel polyurethanes (PPFUs) were synthesized based on the PPF‐diol, diisocyanates such as 1,6‐diisocyanatohexane, l ‐lysine diisocyanate, and dicyclohexylmethane diisocyanate, and chain extenders such as 1,4‐butylene glycol and l ‐lysine methyl ester hydrochloride (Lys‐OMe·2HCl). By varying the types of diisocyanates, and chain extenders, and the proportion of hard segments, the PPFUs with tailored properties such as mechanical strength and degradation rate were easily obtained. The synthesized PPFUs had an amorphous structure and slight phase separation with strong hydrogen bonding between the soft segments and the hard segments. The elongation of PPFU elastomers reached over 400% with a slow deformation‐recovery ability. The PPFUs were more sensitive to alkaline (5 M, NaOH) hydrolysis than acid (2 M, HCl) and oxidative (30 vol.%, H2O2) erosion. The tensile strength, deformation‐recovery ability, and glass transition temperature of the PPFUs were improved with the increase of hard segment proportion, while the degradation rate was opposite because of the faster degradation of the soft segments. In vitro culture of smooth muscle cells in the extractant of the PPFUs or on the PPFUs film surface revealed low cytotoxicity and good cytocompatibility in terms of cell viability, adhesion, and proliferation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42065. 相似文献
989.
990.
Dongjian Shi Ming Ni Jinfeng Zeng Jin Ye Peihong Ni Xiaoya Liu Mingqing Chen 《Journal of Materials Science》2015,50(1):168-175
A variety of chemosensors have been reported for detection of metal ions. However, the metal ions could not be separated and removed at the same time for the goal of water purification. This paper presents to detect and remove metal ions from aqueous solution simultaneously by a fluorescence chemosensor and functional magnetic nanoparticles. A novel probe adamantyl (AD)–maleic anhydride (MAH)–rhodamine B (RhB) was designed and synthesized from RhB, ethylene diamine, MAH, and AD. AD–MAH–RhB showed high selectivity and sensitivity to metal ions in aqueous solution. The sensing mechanism was explored by FTIR and mass spectra. The results suggested that AD–MAH–RhB could conjugate with metal ions and form the binding complexes with various stoichiometries of probe and metal ions. Moreover, β-cyclodextrin-modified magnetic nanoparticles (CD-MNP) were fabricated and used as host materials to form inclusion complex of CD-MNP and AD–MAH–RhB-metal ions. Then, the metal ions could be removed by an outer magnet, which were confirmed by fluorescent spectrum. The probe and CD-MNP had the great potential application for sewage treatment. 相似文献